1. Technical Field
The present invention relates to a communication system, a communication method, and a portable machine, and in particular to a communication system, a communication method, and a portable machine which are all related to respective three nodes of a controlled object such as a vehicle, a portable machine, and a portable terminal.
2. Related Art
Currently, systems are generally known, in which a vehicle portable machine (hereinafter, referred to as an “FOB”) of a vehicle user communicates with a vehicle through radio waves. Existing portable terminals, such as portable phones or smartphones, are equipped with a function of relatively short-distance wireless communications, including Bluetooth™ and Near Field Communication (NFC). With this function, wireless communications are widely conducted among a portable terminal and a vehicle or an FOB (for example, see JP 4496511 B1).
Such a wireless communication function is also used to acquire information from a vehicle or operate the vehicle.
For example, U.S. Pat. No. 7,821,383 discloses a technique in which a portable terminal acquires various information regarding a state of a vehicle, such as a voltage drop of a battery, or someone's intrusion into the vehicle, and displays the acquired information on the screen.
JP 2007-046395 A discloses a vehicle information setting device, which conducts wireless communications with a vehicle by using a portable phone as an interface through an FOB, and displays information regarding the vehicle. In addition, the vehicle information setting device is configured to set and control on-board apparatuses (for example, opening or closing of the doors).
In the case where various pieces of information are exchanged among a portable terminal and a vehicle or an FOB as described above, the security measures such as authentication become very important.
JP 2004-088337 A discloses a keyless control method that aims to improve the convenience of a user. In this keyless control method, a portable phone downloads an identification code and the like from an ID management company's server through a public line network, and transmits a registration signal to an on-board controller in a vehicle through short-distance wireless communications. Then, if successfully identifying the identification code, the on-board controller registers a sub-ID of the portable phone, and performs a control operation of the vehicle, such as unlocking of the doors, with the sub-ID.
JP 2007-251557 A discloses an authentication processing system that aims to facilitate the registration of a portable phone with a vehicle authentication device under tight security. In this authentication processing system, first, a portable phone accesses to a vehicle management server to acquire authentication data. In turn, the vehicle detects a user's operation that indicates the start of a registration process, by which a portable phone is registered as an auxiliary key. Then, when detecting the portable phone within a coverage area of short-distance communications, the vehicle receives authentication data from the portable phone. Finally, the vehicle authenticates the portable phone, based on the authentication data.
JP 2010-168849 A discloses a key code management system for vehicles which aims to reduce a risk of leaking a key code. In this key code management system, a vehicle communicates with an authentication card to acquire an authentication card ID recorded in this authentication card. Then, the vehicle compares the acquired authentication card ID with that stored in the vehicle itself, and creates a key code when both card IDs match. In this case, the vehicle and the portable phone communicate with each other, and the portable phone stores the key code having been stored in the vehicle. After that, the vehicle determines whether or not the registration of a key code is correct, and completes the registration if this registration is correct.
JP 2009-264010 A discloses a remote control device that aims to further enhance the difficulty of decoding a transmission code containing an encrypted ID code. In this remote control device, a control circuit in a transmitter encrypts a rolling code, based on a key code unique to a vehicle. Then, the control circuit adds, to the encrypted rolling code, an additional data whose a bit length changes for every transmission, thereby generating a variable encrypted rolling code. Finally, the control circuit encrypts an ID code with the variable encrypted rolling code, thus generating a transmission code.
JP 2007-085007 A discloses a vehicle communication keylock system that aims to improve the reliability by making the falsification of a key more difficult. In this vehicle communication keylock system, encrypted data are exchanged between a main machine and a sub machine through two-way communications. Specifically, encryption methods and encrypted keys to be used differ every time the communications are conducted.
It is, however, undesirable that “keys” for authentication be exchanged through a public line, such as the Internet, from the viewpoint of security. Furthermore, because in general, a portable terminal is cheaper than a vehicle such as an automobile, there are cases that a portable terminal is frequently replaced by a new one. It is very inconvenient for a user to always bring a new portable terminal to, for example, a dealer of the vehicle and to perform the registration or deletion/re-registration processing. Moreover, when different keys are used every time the communications are conducted between, for example, a vehicle and a portable terminal as in a system using a rolling code, the relationship is not fixed between the vehicle and the FOB. Therefore, whenever buying a portable phone, a user is required to perform a necessary procedure for an application of the new portable phone. This procedure can be unsatisfactory.